The present invention relates to a replacement tube for the lacrimal drainage ducts and, more particularly, to a replacement tube which, when implanted within the tear duct of a patient, will not subsequently become dislodged or rejected.
Lacrimal fluid or tears are continuously supplied from the lacrimal gland, located laterally and superiorly of the eye, through the upper lacrimal duct, and to the conjunctival sac in which the eyeball is partially encased. Hence, the lacrimal fluid washes across the sclera and other conjunctival components, and also the cornea. Under normal conditions, excess lacrimal fluid beyond that which is retained by the eye and conjunctiva is drained from the inner canthus to the nasal passages and to the inferior nasal meatus in particular. The flow of lacrimal fluid, under normal conditions, is continuous but in varying amounts. In normal function, any excessive lacrimal fluid will brim over the eyelids in the form of tears. At other times, the excess fluid is drained through a network of passageways commencing with the puncta which appear as a small papilla adjacent the inner canthus or inner corner of the eye. Therefore, the lacrimal fluid is collected in the lacrimal sac by a number of canaliculi connecting the puncta with the lacrimal sac. The canaliculi run inferiorly then medially to the lacrimal sac. The lacrimal sac is drained through its extension, the nasolacrimal duct which passes into the inferior nasal meatus for this purpose. This network of passages is referred to herein and in the claims as the lacrimal drainage ducts.
Quite often a permanent closure occurs in the canaliculi, the lacrimal sac, or the nasolacrimal duct, whereupon the lacrimal fluid no longer can be disposed of in the normal manner. Such closure or stenosis can result from congenital anomalies, accident, inflammation or other disease, as well as advancing age. In addition, the canaliculi may become scarred from conjunctival infection. Epiphora likewise can result from blockage of the canaliculi by a cilium or by streptothrix concretions. In severe cases permanent stenosis occurs and a dacryocystorhinostomy is indicated.
Upon occurrence of blockage in the lacrimal drainage ducts, the eye, of course, is continuously brimming over with tears much to the discomfort, annoyance, and embarrassment of the individual so affected. A much more serious consequence is the potential for stagnating tears that may result in infection and inflammatory irritation of the mucous membrane with proliferation of the epithelium, hyperemia, and a purulent exudation into the conjunctiva.
In some cases the defective portion of the lacrimal drainage system can be reconstructed by surgery, as when performing a dacryocystorhinostomy. If blockage occurs in the nasolacrimal duct, for example, the latter can be removed, and the lacrimal sac cavity can be joined directly with the nasal fossa (mucosa) after removing a segment of the nasal bone and periosteum to restore drainage of the tears in a more or less natural manner. In most cases, however, removal of the entire lacrimal drainage system and replacement thereof with a mechanical contrivance or replacement tube, by dacryocystorhinostomy, is indicated. Although such operations are frequently performed, they are seldom entirely successful. At least two prominent difficulties have been almost uniformly experienced with such operations in the past. In the first instance, although the nasal bone apparently heals about the lower end portion of the replacement tube, the replacement tube gradually is rejected from the bone and flesh of the patient. Secondly, the patient's flesh heals over the upper end of the replacement tube at the inner canthus and must be reopened periodically.
One approach to the solution of the above described problems appears in the patent to Alkio, U.S. Pat. No. 2,154,968 (1939). Said patent discloses a method of enlarging and draining the lacrimal duct. This method comprises the inserting of a tube in said duct in order to preliminarily enlarge the same, thereafter inserting a spiral cannula into said duct, through the nose and behind the tube. The tube and the cannula are then drawn upwardly in the duct. The tube is then removed with the cannula remaining in the duct for drainage of secretions between the spirals of the cannula. In essence, the method of Alkio comprises the use of thin metal wire formed in spiral shape which is utilized as a support and drainage means for a damaged lacrimal duct.
A patent to Parker, U.S. Pat. No. 3,726,284 (1973) discloses a replacement tube for the lacrimal drainage ducts which tube includes a pair of elongated end portions. The replacement tube includes an expanded central portion having a drainage passage which adjoins adjacent ends of the end portions. Each of said end portions exhibits a drain passage extending therethrough and communicating with the expanded portion. Said portion forms relatively abrupt junctions at generally opposite sides thereof in order to prevent rejection of the replacement tube.
Other art of this general category appears in Class 128, Sub-Class 350.